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Pre amps, how do they work?

Discussion in 'Amps and Cabs [BG]' started by Rakie, Dec 27, 2006.

  1. Rakie

    Rakie Let me take you down, 'cause I'm going to...

    I searched and couldnt find exactly my question, apparently my understanding of pre-amps is below average :bawl:

    So... does a pre-amp change the tone of a head? Like, what if say you have a Mag 300 and love the tone and sound. Why would you get a pre-amp? And when you get it, what will it do to the sound you love? CHange it completely? or just let you shape it more then the EQ in the head?

    Sorry i know these questions are kinda weak but, id like to know this stuff.

    <-- Needs some type of book for dummies.

    thanks !
  2. Do you mean a footpedal preamp?

    Because your mag 300 has a built in pre. The preamp is the section on your amp including the gain (boosts weak signal from bass leading into amp), the equilizer, any compression where applicable. The point of the pre is to boost the weak signal coming from the bass to help utilize max power from the amp. It is also used to help tone shape.
    In essance, if you love the sound of your mag 300, most of the tone you love is due to the pre amp. Not all of it, most of it. Any preamp you use before the built in would mostly boost the signal even more, possibly expand your tone shaping capabilities. But most of your tone is produced first by the bass itself and then the amplifier of your choosing.

    I am sure that this is a rudimentary overview at best. So I am sure others will be along shortly to fill the gaps

  3. Ibanezzer


    Aug 12, 2004
    Dayton, Ohio
    you say that you are using a Mag (Ashdown), that means that you are using what is called a "bass head" (or bass specific amp).

    A "pre-amp" is used in setups where you would purchase a dedicated power-amp (where all it does it power a line level signal, without any eq'ing or tone modication at all, example would be a crown, qsc, etc). The pre-amp gives the tone shaping and also boosts the bass's output level to that which the power amp could utilize.

    Your Mag has a pre-amp and a power-amp built into the unit, a bass head basically has eveyrthing built in, you would not neeed a pre-amp in that setup. If you found that you somehow hated the sound of the mag at a later point you could buy a pre-amp and stick it in the return of the fx loop (if it has one) and use the pre-amp's tone, this would in effect turn your mag into just a poweramp since you would be bypassing its internal preamp.

    I'm using a pre/poweramp setup (just bought a new preamp actually). If I were to plug my bass directly into the input of the poweramp, then I get volumes that are similiar to that of maybe a small 5 or 10 watt bass amp when my 2400 watt poweramp is cranked. The point of the pre is to boost the signal so that their is a high enough (electically) signal to push the poweramp to its potential. WHen using a pre-amp and then goign to my poweramp I barely need to turn up past a quarter to get really loud decent sound out of it.

    hope this helps, I just learned all about pre's over the last few weeks as I finally bought a real pre-amp to replace my boss gt6b effects board (i plan to use it for fx only not a preamp too).

  4. Rakie

    Rakie Let me take you down, 'cause I'm going to...

    Awesome, thanks a lot guys. Thats kinda what I was thinkin git was but not sure.

    About bypassing the internal Pre, i noticed lots of people with heads ran other things like the BBE / Tech 21 / Sansamp and all that, I wasnt sure if it replaced the sound, OR, if it just made the sound more versitile in some way.

    Anyways, thanks again. I started looking into racks and all this stuff i never bothered with the only thing i was pretty sure im picking up is one of the Furman Power conditioners, hehe.
  5. BbbyBld


    Oct 13, 2005
    Meridian, MS
    Besides what has already been said...

    Someone may run a preamp if they wanted to use a parallel bass rig. They may want a foot-switchable boost for solos, or they may use the DI in the preamp because they like it better than the one in the amp. As far as "changing the sound completely," it wouldn't have to, but pretty much anything you add to the signal chain will effect it in some way.
  6. Rakie

    Rakie Let me take you down, 'cause I'm going to...

    I remember reading something about a setup some guy had, he ran a Sadowsky pre amp for when he was in the mix, and went to his normal head tone for things where he was either soloing or just standing out. Idk too much about Sadowsky basses except i keep hearing they're amazing in the mix and lack tone while played Solo.

    Of course, i wouldnt know personally i cant afford a Sadowsky, heheh.
  7. bobbybass85


    Dec 19, 2005
    Nashville, TN
    Ok so i know this isn't really amp related but how does an on-board preamp work and how is it different?
  8. BbbyBld


    Oct 13, 2005
    Meridian, MS
    There really is no difference, they work the same way, but are in a seperate package. Some companies even re-package preamps from popular heads to be sold seperately.
  9. skoti89


    Feb 23, 2006
    Chico, Ca
    haha, nice and well explained
  10. Rakie

    Rakie Let me take you down, 'cause I'm going to...

    Yeah, Ashdown sells a preamp, i think they may sell the ABM Evo one, and maybe the mag one as well seperate.

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